Printers are common peripheral devices attached to computers. A printer allows a computer user to make a hard copy of documents that are created in a variety of applications and programs on a computer. To function properly, a channel of communication is established (e.g., via a network connection) between the printer and the computer to enable the printer to receive commands and information from the host computer. Once a connection is established between a workstation and the printer, printing software is implemented at a print server to manage a print job from order entry and management through the complete printing process.
In high-speed production printers, software maintenance and/or upgrade changes are often necessary to improve printer performance. After such changes however, the print quality must be verified. One method of verifying print quality is to compare a bitmap file of page images generated during a print job prior to the changes with a bitmap file of the same print job generated after the changes.
In such a method, bitmap compare software is used to examine page images generated by a printer to ensure that changes do not affect printed results, or to ensure that defects have been fixed. In automated bitmap comparisons, different methods may be used to detect different types of problems. Such methods include an Exact method in which pixels must be identical, a Neighbor method that allows small shifts in position, a Fuzzy method which permits small shifts in position and different anti-aliasing a Threshold method that allows for small shifts in gray or color levels, as well as Coverage and Bounding Box methods. A problem with each of these methods is that they are global and do not characterize the distribution of miscompared pixels.
Therefore, mechanism to calculate a value that characterizes the global distribution of miscompared pixels is desired.